Review of Linux Compatibility

The Edimax EW-7811UN USB Wireless adapter has the USB ID 7392:7811 and is fully supported since Ubuntu 11.10. The stick can be used with WPA2 encryption and 802.11n. The device is also shipped with different branding, although the hardware is identical. The following devices are identical to the Edimax EW-7811UN:

Realtek Module 8192cu

If the EW-7811UN stick is used with older distributions it might be necessary to use the Edimax original drivers together with NdisWrapper.
Furthermore, one can use the original Realtek drivers. If the Realtek driver is used instead of the module which is part of the standard kernel, the automatic loading of the kernel module has to be inhibited. To achieve this, the rtl8192cu driver provided by the standard kernel has to be blacklisted in the file /etc/modprobe.d/blacklist.conf by adding the following line:

blacklist rtl8192cu

The module from the Realtek homepage is called 8192cu and has to be compiled by hand. Under Ubuntu compilation will need the build-essentials to be installed:

sudo apt-get install build-essential

Compilation will be achieved by the install script that is part of the downloaded file:

sudo sh install.sh

The compiled driver can be loaded by the command

sudo modprobe 8192cu

Due to a bug in the power management of the 8192cu driver the connection can drop if the device is set to power save mode. This can be seen in the log files:

I use it as a backup for the internal WiFi chipset, which sometimes has problems to connect with certain (not IEEE standard obeying) access points. Due to its smal size the EW-7811Un is ideal to use during traveling. Range is fine and comparable to the range of the chipset included in my notebook.

I’ve been having problems with this particular adapter in Pinguy 12.04 (Ubuntu derivative), disconnecting and reconnecting to my BT router at random, sometimes staying stable for hours at a time, sometimes disconnecting in minutes or seconds. Signal strength was reported as 67%. Browsing the internet whilst downloading a (legal) torrent made it deauthenticate 8 times out of 10. Searching for the error codes made me suspect it is not limited to this chipset.

I tried applying the fix given in the article, creating the line in a new 8192cu.conf when I didn’t find it. No change.

I have been receiving reason=6 (Client attempted to transfer data before it was authenticated) and reason=3 (The access point went offline, deauthenticating the client), the former more than the latter.

Fixes: Disabling security on the access point altogether appears to work, as does using netcfg on the command line to configure the connection and/or removing wicd. Ensuring there is only one network daemon would be something to try as well.

It’d be helpful to let users know which versions of the most common ‘parent’ distros — Debian, Fedora, OpenSUSE — it became supported in. That way, the Ubuntu crowd *and* most of the Linux users that rely on another distro. (I’m fairly sure that if you add up the users of all non-Ubuntu distros, you get a larger number than *just* Ubuntu & its descendants…)

We normally try to give information for all common distributions including Debian, Fedora, and OpenSUSE. However, since Ubuntu is the most popular one, details for non-Ubuntu distros are often harder to find. Therefore, the data base often looks very Ubuntu centric although this is not our intention. If possible, we try to define compatibility based on kernel versions and not distributions because this information is more universal.

Start new Discussion

Please use the comment section to submit corrections to the article as well as relevant excerpts of lspci, lsusb, lshw, dmesg e.t.c.
Furthermore, use the section for the exchange of experiences with this hardware component or search for configuration help from other owners of this hardware.